Single-phase alternating-current motor.



No758,668- 7 PATBNTED MAY 3, 1904.

B. e. LAMMB. SINGLE PHASE ALTERNATING CURRENT MOTOR.

v u'rmonlon TILED 00131. 1902. RENEWED SEPT. 24. 1903" no 110mm.

WITNESSES:

Patented May 3, 1904..

UNIT STATES I PATENT OFFICE.

BENJAMIN G. LAMME, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A COR- PORATION OF PENNSYLVANIA.

SINGLE-PHASE ALT ERNATING-C URRENT MOTOR- SPECIFICATION forming part of Letters Patent No. 758,668, dated May 3, 1904. Application filed October 31, 1902. Renewed September 24, 1903. Serial No. 174,522- (No model.)

To all whom it may concern.-

Be it known that I, BENJAMIN G. LAMME, a citizen of the United States, and a resident of Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Single-Phase Alternating-Current Motors, of which the following is a specification.

My invention relates to alternating-current motors of the type in which the field-magnet and armature-coils are connected in series relation by means of commutators and which are operated by means of single-phase currents.

The object of my invention is to provide a motor of the character above indicated with high-resistance conductors between the armature-coils and the commutator-bars, which shall be advantageously disposed with reference to the other parts of the motor.

In motors of the type to which my present invention belongs the armature-winding is of the closed-coil parallel-circuit type and is closed upon itself, and as the magnetic field of the motor is alternating any short-circuited turn through which the magnetic flux from a field-pole passes will have a secondary current set up in it. By the well-known laws of the transformer the ampere-turns in such shortcircuited secondary will approximate the ampore-turns in the primary winding, which is in this case the field-magnet winding. By reason of the character of the armature-winding certain of its coils are shortcircuited through the brushes when the adjacent commutator-bars,'to which the ends of the coils are connected, are bridged thereby, and when the brushes are located in neutral positions or without lead the short-circuited turns surround the paths of. the magnetic flux, and are therefore good secondary circuits in which under ordinary conditions relatively large secondary currents are set up by induction. This is the principal cause of the excessive sparking in series motors of ordinary construction when it is attempted to operate them upon an alternating-current circuit. In order to obviate destructive sparking, the current in the OI't-Oircuited turns of the armature-coils should be limited to an amountmaterially less than what would normally flow. This may be effected by inserting a definite amount of resistance in each of the leads between. the.

closed winding and the commutator-bars. The working currents in the armature-winding will not pass through these resistances except at the bars in contact with the brushes, because the armatu're-winding is closed upon itself inside or beyond the resistance leads.- Consequently the loss in the winding due to the introduction of the resistance may be relatively small, and when the armature is rotating this loss is distributed successively through all the resistances, thus making the average loss per resistance lead very small. Various ways of introducing such a resistance may be employed; but to provide the desired amount of resistance and at thesame time so dispose it that it will be securely supported under the comparatively rapid rotation of the armature is a somewhat difficult problem.

In motors of large power employed for operating railway-vehicles the space allowable for the motors is extremely restricted, and hence it is a matter of material importance to so dispose the several elements of the motor as to secure the desired ventilation and general efficiency without occupying more than the allowable amount of space.

Referring now to the accompanying drawings, Figure 1 is a longitudinal section through an armature and commutator constructed in accordance with my invention, the ends of the armature-shaft being broken away. Fig. 2 is a diagram of one of the armature-coils.

The skeleton frame or spider 1 of the armature is mounted upon and keyed to the shaft 2 inthe usual manner and is provided with an extension 3, on which is mounted the commutator 4E. The laminated core 5 is mount ed and suitably fastened upon the frame or spider 1 and is provided with ventilatingducts 6 and with slots 7 in which are mounted the coils 8, these coils being connected at the end remote from the commutator A by means of suitable connectors 9, so as to form a closed parallel-circuit winding, the winding being also joined by means of conductors 10 to balancing-rings 11, in order to properly balance the magnetic circuit, in the manner set forth in Patent No. 573,009, granted to the Westinghouse Electric & Manufacturing Company December 15, 1896, upon an application filed by me.

Each coil 8 is connected to its appropriate commutator-bar by means of a conductor 12 of relatively high resistance and a connector 13, one end of which is fastened to the corresponding commutator-bar and the other end of which is fastened to the corresponding end of the resistance conductor 12. This conduetor 12 may be formed of German silver or other suitable high-resistance material and is located in the bottom of the slot 7, it being provided with a suitable insulating-sheath in the same manner as are the corresponding portions of the coils 8. There is, obviously, one of these resistance-eonductors 12 in each slot, and since it is located in the bottom of the slot it is advantageously disposed both as regards the security of its position and also because it does not interfere in any way with the proper disposition of the other parts of the machine.

I claim as my invention 1. In an alternating current motor, the combination with a commutator, of an armature-core provided with slots, a parallel closed circuit-winding and high-resistance leads connecting said winding with the commutatorbars, the coils constituting the winding and the high-resistance leads being located in the core-slots.

2. In an alternating current motor, the combination with a commutator and an armature core provided with slots, of coils and high-resistance leads located in said slots, the said coils and leads being connected together at the end of the armature remote from the commutator.

8. In an alternating current motor, the combination with a commutator and an armature-core provided with slots, of coils and high-resistanceleads located in said slots, said leads being located in the bottoms of the slots and connected to the armature-coils at the ends remote from the commutator.

4. In an electrical machine, the combination with a commutator, of a slotted armaturecore having coils located in the core-slots and connected in parallel, closed-coil arrangement at the end remote from the commutator and high-resistance leads connecting the commutator-bars with the remote ends of the coils and located in the core-slots.

In testimony whereof I have hereunto sub scribed my name this 25th day of October,

- BENJ. G. LAMME. l/Vitnesses:

J. O. MORSE, BIRNEY HINns. 

